Sample tube rack



FIG. 1 is a front perspective view of a sample tube rack;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a side elevational view thereof;

FIG. 5 is an opposite side elevational view thereof;

FIG. 6 is a bottom plan view thereof; and,

FIG. 7 is a rear elevational view thereof. 

The ornamental design for a sample tube rack, as shown and described. 